Fleetwood takes control in Durban
Briton Tommy Fleetwood in action in Vilamoura, southern Portugal on October 11, 2013
The Englishman, seeking his second win on the European Tour, produced four birdies and a lone bogey to move to a ten under par total of 206.
Breathing down his neck with a share of second on 207 were France's Victor Dubuisson and Dutchman Joost Luiten, with last year's winner Louis Oosthuizen two off the pace despite a triple bogey seven at the 16th.
Fleetwood, who opened his Tour account in the Johnnie Walker Championship at Gleneagles last year, was satisfied to be in the lead after a demanding day's play.
"I played four or five really good holes, but obviously the rest of it I struggled," the 22-year-old told www.europeantour.com.
"You miss your tee shots you're always going to struggle for pars. I made one bogey but it was always coming at some point so I was quite cool and calm at the end of it.
"Three under around this golf course when you're not on your game is an absolutely brilliant score, and so I think it's showing I'm maturing as a golfer."
He is hoping a win in Durban can set him up for an "exceptional" year leading to a place in Paul McGinley's Ryder Cup team.
Dubuisson, third on the European Ryder Cup points list, had his short game to thank for a solid third round.
Local hope Oosthuizen meanwhile was leading the pack with three holes to go before his triple bogey slip-up after striking his second into deep undergrowth and declaring it unplayable.
"It's frustrating that I finally got my seven birdies, which you need to do around this course, but made too many bogeys," the 2010 Open Champion said.
"I was not great off the tee and hit a few wayward shots but I'm still happy to be right in there."
Fellow South African Braden Grace is a shot further back on seven under with Wales' Jamie Donaldson another stroke away alongside France's Raphael Jacquelin.